[Qemu-devel] [PULL 32/39] target-ppc: Rework SLB page size lookup

[David Gibson]

Currently, the ppc_hash64_page_shift() function looks up a page size based
on information in an SLB entry.  It open codes the bit translation for
existing CPUs, however different CPU models can have different SLB
encodings.  We already store those in the 'sps' table in CPUPPCState, but
we don't currently enforce that that actually matches the logic in
ppc_hash64_page_shift.

This patch reworks lookup of page size from SLB in several ways:
  * ppc_store_slb() will now fail (triggering an illegal instruction
    exception) if given a bad SLB page size encoding
  * On success ppc_store_slb() stores a pointer to the relevant entry in
    the page size table in the SLB entry.  This is looked up directly from
    the published table of page size encodings, so can't get out ot sync.
  * ppc_hash64_htab_lookup() and others now use this precached page size
    information rather than decoding the SLB values
  * Now that callers have easy access to the page_shift,
    ppc_hash64_pte_raddr() amounts to just a deposit64(), so remove it and
    have the callers use deposit64() directly.

Signed-off-by: David Gibson <address@hidden>
Acked-by: Benjamin Herrenschmidt <address@hidden>
Reviewed-by: Alexander Graf <address@hidden>
---
 target-ppc/cpu.h        |  1 +
 target-ppc/machine.c    | 20 +++++++++++++
 target-ppc/mmu-hash64.c | 74 +++++++++++++++++++++++--------------------------
 3 files changed, 56 insertions(+), 39 deletions(-)

diff --git a/target-ppc/cpu.h b/target-ppc/cpu.h
index 2bc96b4..0820390 100644
--- a/target-ppc/cpu.h
+++ b/target-ppc/cpu.h
@@ -419,6 +419,7 @@ typedef struct ppc_slb_t ppc_slb_t;
 struct ppc_slb_t {
     uint64_t esid;
     uint64_t vsid;
+    const struct ppc_one_seg_page_size *sps;
 };
 
 #define MAX_SLB_ENTRIES         64
diff --git a/target-ppc/machine.c b/target-ppc/machine.c
index b61c060..ca62d3e 100644
--- a/target-ppc/machine.c
+++ b/target-ppc/machine.c
@@ -2,6 +2,7 @@
 #include "hw/boards.h"
 #include "sysemu/kvm.h"
 #include "helper_regs.h"
+#include "mmu-hash64.h"
 
 static int cpu_load_old(QEMUFile *f, void *opaque, int version_id)
 {
@@ -352,11 +353,30 @@ static bool slb_needed(void *opaque)
     return (cpu->env.mmu_model & POWERPC_MMU_64);
 }
 
+static int slb_post_load(void *opaque, int version_id)
+{
+    PowerPCCPU *cpu = opaque;
+    CPUPPCState *env = &cpu->env;
+    int i;
+
+    /* We've pulled in the raw esid and vsid values from the migration
+     * stream, but we need to recompute the page size pointers */
+    for (i = 0; i < env->slb_nr; i++) {
+        if (ppc_store_slb(cpu, i, env->slb[i].esid, env->slb[i].vsid) < 0) {
+            /* Migration source had bad values in its SLB */
+            return -1;
+        }
+    }
+
+    return 0;
+}
+
 static const VMStateDescription vmstate_slb = {
     .name = "cpu/slb",
     .version_id = 1,
     .minimum_version_id = 1,
     .needed = slb_needed,
+    .post_load = slb_post_load,
     .fields = (VMStateField[]) {
         VMSTATE_INT32_EQUAL(env.slb_nr, PowerPCCPU),
         VMSTATE_SLB_ARRAY(env.slb, PowerPCCPU, MAX_SLB_ENTRIES),
diff --git a/target-ppc/mmu-hash64.c b/target-ppc/mmu-hash64.c
index 6e05643..b784791 100644
--- a/target-ppc/mmu-hash64.c
+++ b/target-ppc/mmu-hash64.c
@@ -19,6 +19,7 @@
  */
 #include "cpu.h"
 #include "exec/helper-proto.h"
+#include "qemu/error-report.h"
 #include "sysemu/kvm.h"
 #include "kvm_ppc.h"
 #include "mmu-hash64.h"
@@ -140,6 +141,8 @@ int ppc_store_slb(PowerPCCPU *cpu, target_ulong slot,
 {
     CPUPPCState *env = &cpu->env;
     ppc_slb_t *slb = &env->slb[slot];
+    const struct ppc_one_seg_page_size *sps = NULL;
+    int i;
 
     if (slot >= env->slb_nr) {
         return -1; /* Bad slot number */
@@ -154,8 +157,29 @@ int ppc_store_slb(PowerPCCPU *cpu, target_ulong slot,
         return -1; /* 1T segment on MMU that doesn't support it */
     }
 
+    for (i = 0; i < PPC_PAGE_SIZES_MAX_SZ; i++) {
+        const struct ppc_one_seg_page_size *sps1 = &env->sps.sps[i];
+
+        if (!sps1->page_shift) {
+            break;
+        }
+
+        if ((vsid & SLB_VSID_LLP_MASK) == sps1->slb_enc) {
+            sps = sps1;
+            break;
+        }
+    }
+
+    if (!sps) {
+        error_report("Bad page size encoding in SLB store: slot "TARGET_FMT_lu
+                     " esid 0x"TARGET_FMT_lx" vsid 0x"TARGET_FMT_lx,
+                     slot, esid, vsid);
+        return -1;
+    }
+
     slb->esid = esid;
     slb->vsid = vsid;
+    slb->sps = sps;
 
     LOG_SLB("%s: %d " TARGET_FMT_lx " - " TARGET_FMT_lx " => %016" PRIx64
             " %016" PRIx64 "\n", __func__, slot, esid, vsid,
@@ -394,24 +418,6 @@ static hwaddr ppc_hash64_pteg_search(PowerPCCPU *cpu, 
hwaddr hash,
     return -1;
 }
 
-static uint64_t ppc_hash64_page_shift(ppc_slb_t *slb)
-{
-    uint64_t epnshift;
-
-    /* Page size according to the SLB, which we use to generate the
-     * EPN for hash table lookup..  When we implement more recent MMU
-     * extensions this might be different from the actual page size
-     * encoded in the PTE */
-    if ((slb->vsid & SLB_VSID_LLP_MASK) == SLB_VSID_4K) {
-        epnshift = TARGET_PAGE_BITS;
-    } else if ((slb->vsid & SLB_VSID_LLP_MASK) == SLB_VSID_64K) {
-        epnshift = TARGET_PAGE_BITS_64K;
-    } else {
-        epnshift = TARGET_PAGE_BITS_16M;
-    }
-    return epnshift;
-}
-
 static hwaddr ppc_hash64_htab_lookup(PowerPCCPU *cpu,
                                      ppc_slb_t *slb, target_ulong eaddr,
                                      ppc_hash_pte64_t *pte)
@@ -419,21 +425,24 @@ static hwaddr ppc_hash64_htab_lookup(PowerPCCPU *cpu,
     CPUPPCState *env = &cpu->env;
     hwaddr pte_offset;
     hwaddr hash;
-    uint64_t vsid, epnshift, epnmask, epn, ptem;
+    uint64_t vsid, epnmask, epn, ptem;
+
+    /* The SLB store path should prevent any bad page size encodings
+     * getting in there, so: */
+    assert(slb->sps);
 
-    epnshift = ppc_hash64_page_shift(slb);
-    epnmask = ~((1ULL << epnshift) - 1);
+    epnmask = ~((1ULL << slb->sps->page_shift) - 1);
 
     if (slb->vsid & SLB_VSID_B) {
         /* 1TB segment */
         vsid = (slb->vsid & SLB_VSID_VSID) >> SLB_VSID_SHIFT_1T;
         epn = (eaddr & ~SEGMENT_MASK_1T) & epnmask;
-        hash = vsid ^ (vsid << 25) ^ (epn >> epnshift);
+        hash = vsid ^ (vsid << 25) ^ (epn >> slb->sps->page_shift);
     } else {
         /* 256M segment */
         vsid = (slb->vsid & SLB_VSID_VSID) >> SLB_VSID_SHIFT;
         epn = (eaddr & ~SEGMENT_MASK_256M) & epnmask;
-        hash = vsid ^ (epn >> epnshift);
+        hash = vsid ^ (epn >> slb->sps->page_shift);
     }
     ptem = (slb->vsid & SLB_VSID_PTEM) | ((epn >> 16) & HPTE64_V_AVPN);
 
@@ -465,20 +474,6 @@ static hwaddr ppc_hash64_htab_lookup(PowerPCCPU *cpu,
     return pte_offset;
 }
 
-static hwaddr ppc_hash64_pte_raddr(ppc_slb_t *slb, ppc_hash_pte64_t pte,
-                                   target_ulong eaddr)
-{
-    hwaddr mask;
-    int target_page_bits;
-    hwaddr rpn = pte.pte1 & HPTE64_R_RPN;
-    /*
-     * We support 4K, 64K and 16M now
-     */
-    target_page_bits = ppc_hash64_page_shift(slb);
-    mask = (1ULL << target_page_bits) - 1;
-    return (rpn & ~mask) | (eaddr & mask);
-}
-
 int ppc_hash64_handle_mmu_fault(PowerPCCPU *cpu, target_ulong eaddr,
                                 int rwx, int mmu_idx)
 {
@@ -600,7 +595,7 @@ int ppc_hash64_handle_mmu_fault(PowerPCCPU *cpu, 
target_ulong eaddr,
 
     /* 7. Determine the real address from the PTE */
 
-    raddr = ppc_hash64_pte_raddr(slb, pte, eaddr);
+    raddr = deposit64(pte.pte1 & HPTE64_R_RPN, 0, slb->sps->page_shift, eaddr);
 
     tlb_set_page(cs, eaddr & TARGET_PAGE_MASK, raddr & TARGET_PAGE_MASK,
                  prot, mmu_idx, TARGET_PAGE_SIZE);
@@ -630,7 +625,8 @@ hwaddr ppc_hash64_get_phys_page_debug(PowerPCCPU *cpu, 
target_ulong addr)
         return -1;
     }
 
-    return ppc_hash64_pte_raddr(slb, pte, addr) & TARGET_PAGE_MASK;
+    return deposit64(pte.pte1 & HPTE64_R_RPN, 0, slb->sps->page_shift, addr)
+        & TARGET_PAGE_MASK;
 }
 
 void ppc_hash64_store_hpte(PowerPCCPU *cpu,
-- 
2.5.0